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Full vulnerability report · 2023
CVE-2023-6563High confidence

Keycloak: offline session token dos

Red Hat · Red Hat Single Sign-On 7.6 for RHEL 7

Official source articles: Red Hat RHSA-2023:7854 ↗ · Red Hat RHSA-2023:7855 ↗ · Red Hat RHSA-2023:7856 ↗ · Red Hat RHSA-2023:7858 ↗ · Red Hat RHSA-2023:7857 ↗. Check the applicable product and release in the original source.

7.7HighCVSS 3.1
Recommended action
Within 7 days

High technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityHighOperational priority:Critical, raised one band.upgradedsince 22 Sep 2026

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • A structured source references public exploit or proof-of-concept material.
  • EPSS is 1.24% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Increase monitoring for the attack path and post-exploitation behaviour described in the report.

Verification

  1. Confirm that the asset runs Red Hat Red Hat Single Sign-On 7.6 for RHEL 7 and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 3 daysRemediation target: Within 90 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Open-source package ranges1 source-attributed range

These OSV and GitHub advisory ranges apply only to the named package and ecosystem. A listed fixed version is not a universal product patch or proof that an update is installed.

Ecosystem and packageAffected rangeFirst fixed versionEvidence
mavenorg.keycloak:keycloak-model-jpa< 21.0.021.0.0GitHub advisory ↗github reviewed aggregator · 29 Dec 2023
Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
CVE-2023-6563 · CSAF 2.0 · revision 3 · finalRed Hat Product Securitykeycloak: offline session token DoS
14 fixed

The vendor explicitly identifies these products or versions as containing the fix.

  • rh-sso7-keycloak-0:18.0.11-2.redhat_00003.1.el7sso.noarch as a component of Red Hat Single Sign-On 7.6 for RHEL 7 Server
  • rh-sso7-keycloak-0:18.0.11-2.redhat_00003.1.el7sso.src as a component of Red Hat Single Sign-On 7.6 for RHEL 7 Server
  • rh-sso7-keycloak-server-0:18.0.11-2.redhat_00003.1.el7sso.noarch as a component of Red Hat Single Sign-On 7.6 for RHEL 7 Server
  • rh-sso-7/sso7-rhel8-operator-bundle@sha256:4cbf1a09c7207f9f1ffc918b5e8a4adaa89938befc6d75040b3ddd505ab14f6c_amd64 as a component of Middleware Containers for OpenShift
  • rh-sso-7/sso76-openshift-rhel8@sha256:05c8f187d183582102855c12ac856f361cc6a0bbd792675799bfc319694bc662_s390x as a component of Middleware Containers for OpenShift
  • rh-sso-7/sso76-openshift-rhel8@sha256:c65934aa7883ccd9655cd1e7e47899e97470e42cc32bbe5386cc64f88fd26696_ppc64le as a component of Middleware Containers for OpenShift
  • rh-sso-7/sso76-openshift-rhel8@sha256:db235506ce5d840dc139a3cde4114939222df6abb0901efaaff4f9ddbc495b9b_amd64 as a component of Middleware Containers for OpenShift
  • rh-sso7-keycloak-0:18.0.11-2.redhat_00003.1.el8sso.noarch as a component of Red Hat Single Sign-On 7.6 for RHEL 8
  • rh-sso7-keycloak-0:18.0.11-2.redhat_00003.1.el8sso.src as a component of Red Hat Single Sign-On 7.6 for RHEL 8
  • rh-sso7-keycloak-server-0:18.0.11-2.redhat_00003.1.el8sso.noarch as a component of Red Hat Single Sign-On 7.6 for RHEL 8
  • rh-sso7-keycloak-0:18.0.11-2.redhat_00003.1.el9sso.noarch as a component of Red Hat Single Sign-On 7.6 for RHEL 9
  • rh-sso7-keycloak-0:18.0.11-2.redhat_00003.1.el9sso.src as a component of Red Hat Single Sign-On 7.6 for RHEL 9
Summary
An unconstrained memory consumption vulnerability was discovered in Keycloak. It can be triggered in environments which have millions of offline tokens (> 500,000 users with each having at least 2 saved sessions). If an attacker creates two or more user sessions and then open the "consents" tab of the admin User Interface, the UI attempts to load a huge number of offline client sessions leading to excessive memory and CPU consumption which could potentially crash the entire system.
Remediation
Before applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://access.redhat.com/articles/11258
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2023-3108

No EUVD known-exploited evidence

An unconstrained memory consumption vulnerability was discovered in Keycloak. It can be triggered in environments which have millions of offline tokens (> 500,000 users with each having at least 2 saved sessions). If an attacker creates two or more user sessions and then open the "consents" tab of the admin User Interface, the UI attempts to load a huge number of offline client sessions leading to excessive memory and CPU consumption which could potentially crash the entire system.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
7.7 · CVSS 3.1
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

An unconstrained memory consumption vulnerability was discovered in Keycloak. It can be triggered in environments which have millions of offline tokens (> 500,000 users with each having at least 2 saved sessions). If an attacker creates two or more user sessions and then open the "consents" tab of the admin User Interface, the UI attempts to load a huge number of offline client sessions leading to excessive memory and CPU consumption which could potentially crash the entire system.

What

An unconstrained memory consumption vulnerability was discovered in Keycloak. It can be triggered in environments which have millions of offline tokens (> 500,000 users with each having at least 2 saved sessions). If an attacker creates two or more user sessions and then open the "consents" tab of the admin User Interface, the UI attempts to load a huge number of offline client sessions leading to excessive memory and CPU consumption which could potentially crash the entire system.

Why

The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

How

An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may disrupt the affected service.

What

An unconstrained memory consumption vulnerability was discovered in Keycloak. It can be triggered in environments which have millions of offline tokens (> 500,000 users with each having at least 2 saved sessions). If an attacker creates two or more user sessions and then open the "consents" tab of the admin User Interface, the UI attempts to load a huge number of offline client sessions leading to excessive memory and CPU consumption which could potentially crash the entire system.

Why

The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

How

An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may disrupt the affected service.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
Reference recorded

A structured CVE source labels at least one public reference as exploit material. BlackTree has not independently validated that it is safe, reliable or weaponised.

Likely attack path
a network path → Allocation of Resources Without Limits or Throttling → disrupt the affected service
Attack surface
Network
Privileges required
Low: a basic authenticated account is required
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Changed: exploitation can affect a different security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-770 ↗

CWE-770: Allocation of Resources Without Limits or Throttling. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRLowPrivileges required: The attacker needs basic user-level privileges.UINoneUser interaction: No action by another user is required.SChangedScope: The attack can affect a component governed by a different security authority.CNoneConfidentiality impact: No direct loss is represented by this metric.INoneIntegrity impact: No direct loss is represented by this metric.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
Stolen credentials, tokens and legitimate administration functions may provide continued access without deploying a large custom toolset.
NetworkDenial of serviceCWE-770Public exploit reference
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2023-3108Official EUVD mapping

An unconstrained memory consumption vulnerability was discovered in Keycloak. It can be triggered in environments which have millions of offline tokens (> 500,000 users with each having at least 2 saved sessions). If an attacker creates two or more user sessions and then open the "consents" tab of the admin User Interface, the UI attempts to load a huge number of offline client sessions leading to excessive memory and CPU consumption which could potentially crash the entire system.

Official EUVD record ↗
BSI · German · WID-SEC-2023-3156Keycloak: Mehrere Schwachstellen

Ein entfernter, anonymer oder authentisierter Angreifer kann mehrere Schwachstellen in Keycloak ausnutzen, um Sicherheitsvorkehrungen zu umgehen oder einen Denial of Service zu verursachen.

Official advisory ↗
Cyber Security Agency of Singapore · English · CSA-SB-20231220Security Bulletin 20 Dec 2023

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 20 Dec 2023, published on 20 December 2023. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2023-023972複数のレッドハット製品における制限またはスロットリング無しのリソースの割り当てに関する脆弱性

Keycloak、Single Sign-On、Red Hat OpenShift Container Platform 等複数のレッドハット製品には、制限またはスロットリング無しのリソースの割り当てに関する脆弱性が存在します。

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
Fixed
Action
Before applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://access.redhat.com/articles/11258
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 14 Dec 2023 · Last source change 22 Sept 2026, 03:27 UTC · CWE-770 · Allocation of Resources Without Limits or Throttling

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2023-3108
Product sourceCNA
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD modified after enrichment

Missing structured fields: affected versions. Missing data is not evidence of low risk; review the primary advisory.

Material change intelligence

What changed after publication

View recent updates ↗
  1. Affected versionsThe structured affected or fixed version information changed.
    Before
    See the vendor and CVE records for the affected range. · Fixed: 0:18.0.11-2.redhat_00003.1.el7sso < *; 0:18.0.11-2.redhat_00003.1.el8sso < *; 0:18.0.11-2.redhat_00003.1.el9sso < *; 7.6-38 < *; 7.6.6-2 < *
    After
    See the vendor and CVE records for the affected range. · Fixed: Red Hat Single Sign-On 7.6 for RHEL 7: 0:18.0.11-2.redhat_00003.1.el7sso < *; Red Hat Single Sign-On 7.6 for RHEL 8: 0:18.0.11-2.redhat_00003.1.el8sso < *; Red Hat Single Sign-On 7.6 for RHEL 9: 0:18.0.11-2.redhat_00003.1.el9sso < *; RHEL-8 based Middleware Containers: 7.6-38 < *, 7.6.6-2 < *
    CNA ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2023-3108↗Vendor CSAF · Red Hat Product Security↗CVE authority or vendor reference · Red Hat RHSA-2023:7854↗Vendor advisory · Red Hat RHSA-2023:7855↗Vendor advisory · Red Hat RHSA-2023:7856↗Vendor advisory · Red Hat RHSA-2023:7858↗Public exploit reference · Red Hat RHSA-2023:7857↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2023-6563 · cve.blacktree.nl